absolute value

The value of a number without regard to
its sign. The absolute value, or modulus, of a real
number, r, is just the distance of the number from zero measured
along the real number line, and is denoted
|r | (read "mod r "). Being a distance, it can't be
negative; so, for example, |3| = |-3| = 3.

The same idea applies to the absolute value of a complex
numbera + ib, except that, in this case, the complex
number is represented by a point on an Argand
diagram. The absolute value, |a + ib|, is the length of
the line from the origin to the given point, and is equal to √(a2
+ b2).